1. Field of the Invention
The present invention relates to a carbon-based soldering or de-soldering tips for use with soldering irons and de-soldering tools, respectively. The tip includes plated soldering surfaces. More particularly, the invention is directed to replaceable soldering and de-soldering tips which are less expensive than standard copper tips, have longer working lives, resist pitting, and eliminate or greatly reduce the problems associated with standard soldering tips. The invention further relates to a method for manufacturing carbon-based soldering and de-soldering tips. The tips are resistent to both high temperatures and corrosion and can be used with all types of soldering irons and de-soldering tools, including temperature-controlled soldering irons and de-soldering tools.
2. Description of the Prior Art
It is well-known that all soldering irons have soldering tips, and the majority of soldering irons are adapted to receive replaceable soldering tips. Replaceable tips are normally inserted into a tip-receiving bore of a soldering iron and are threaded or fixed in place by a set screw or similar mechanical device. It is further known that many temperature-controlled soldering irons include a sensor element extending within the iron's tip-receiving bore. The sensor element fits within a portion of a permanent or replaceable soldering iron tip.
It is also well-known that de-soldering tools have replaceable de-soldering tips which are normally screw-threaded to the tool. These tips include a central tubular vacuum passage through which the melted solder is drawn.
Soldering and de-soldering tips have conventionally been formed from a copper body due, in part, to the heat conductivity of such copper bodies. This standard use of copper as a body of these tips has, however, presented a number of problems. Whenever copper comes into contact with commonly used solders, the solder reacts with the copper and dissolves it. Therefore, copper tips must be plated at least in the solder-wetting portion of the tips. Furthermore, the tubular vacuum passage of a de-soldering tip must be plated or otherwise protected from contact with the melted solder. If it is not, the passage becomes clogged. The plating of the copper base, however, does not completely solve the problem since the coatings wear over time and most often initially have slight imperfections and cracks. Heated solder seeps through such imperfections and worn areas and dissolves the copper base, resulting in cavities in the tip similar to tooth cavities. Thus, copper-based tips often lose their shape and effectiveness after a short period of use.
The use of copper as the base of soldering and de-soldering tips presents an additional and significant problem. Copper, when subjected to the high temperature necessary for soldering or de-soldering, quickly oxidizes. This oxidation damages a tip's surface and, more importantly, often results in a freezing of a replaceable tip to the body of the soldering iron or de-soldering tool at the interface of the tip and the tip-receiving bore. Furthermore, if a soldering iron has a temperature sensor inserted into a bore in the tip, the tip and the temperature sensor often freeze together. This freezing of parts damages the soldering iron itself and often necessitates repair or renders the iron completely unuseable.
The oxidation of a copper tip poses an additional heat transfer problem with soldering tips. To insure proper heat transfer between the heating element and the shank of the soldering tip, the shank must fit snugly in the opening of the heating element. However, the shank of the soldering tip oxidizes at elevated temperatures. The resultant layer of oxide at the interface of the shank and the soldering iron acts as an insulator which decreases the transfer efficiency between the heating element and the soldering tip.
With temperature-controlled soldering irons, the oxidation tends to decrease the sensitivity of control. For the heat sensor to measure the tip temperature accurately, it must fit snugly within the sensor hole. However, the oxidation of the copper at the sensor-tip interface decreases the heat transfer and sensitivity of the control and often chases the tip to freeze to the sensor. This freezing problem is so significant that in most commercial applications the bore receiving the sensor is oversized to eliminate or reduce the freezing. This procedure, however, decreases heat transfer and thus the sensitivity of the temperature control.
One technique used to overcome the freezing problem at the interface of the tip and soldering iron has been to form a stainless steel sleeve over the portion of the copper tip which is received by the soldering iron. While such a stainless steel sleeve has been effective in reducing the freezing problem at the tip-iron interface, the heat transfer properties of the tip are greatly reduced because there is no molecular bond between the stainless steel and the copper. Furthermore, this technique is expensive and does not correct the freezing problem presented at the sensor-tip interface in temperature-controlled soldering irons.
With respect to the foregoing problem at the sensor-tip interface, it has been found that it is difficult, if not impossible, to electroplate the inside of the sensor hole without very expensive individual handling of the tips. Applicant is not aware of any presently available means to economically overcome this freezing problem.
With respect to de-soldering tips, the tubular vacuum passages now on the market often include a stainless steel lining which will not react with the melted solder and can be easily cleaned. Such linings significantly add to the expense of such de-soldering tips.
Because of the miniaturization presently occurring in the electronics field, soldering and de-soldering tips in many applications have decreased substantially in size to permit precise soldering. The demand for smaller soldering tips aggravates the problems presented by the pitting and oxidation of copper-based tips.
Finally, the increasing cost of copper has made copper soldering and de-soldering tips less commercially desirable. The short service life of copper tips increases this expense.